Welding cart for welding a plurality of studs to a beam flange, or other surface

ABSTRACT

Apparatus for welding a plurality of studs to a beam in a predetermined pattern, said apparatus comprising a frame, a plurality of welding tools carried by said frame and having chucks to receive the studs, rear wheel means supporting a rear portion of said frame, a pair of front wheels, a pair of cams rotatable about a common axis in a fixed position relative to said front wheels and engageable with a portion of said frame for raising and lowering said frame, whereby said tools are raised and lowered to facilitate loading of said chucks, and a crank for simultaneously turning said cams to place different portions of said cams of different thicknesses in engagement with said frame portion, said crank extending outwardly from said machine beyond said frame.

United States Patent 218,749 8/1879 Jamin.

WELDING CART FOR WELDING A PLURALITY OF STUDS TO A BEAM FLANGE, OR OTHER SURFACE 7 Claims, 13 Drawing Figs.

Int. Cl B231: 9/20 Field of Search 219/98;

2l9l99;2l9/103, 107, 125, 126; 51/178,241S; 29/(lnquired); 228/(lnquired) References Cited UNITED, STATES PATENTS Primary Examiner-R. F. Staubly Altorneys- Philip E. Parker, James R. O'Connor, John Todd,

Wall & Woughton and Gordon Needleman BIRAC. enparetqs m insj efi 959. 5 3 a beam in a predetermined pattern, said apparatus comprising; frame, a plurality of welding tools carried by said frame and having chucks to receive the studs, rear wheel means supporting a rear portion of said frame, a pair of front wheels, a pair of cams rotatable about a common axis in a fixed position relative to said front wheels and engageable with a portion of said frame for raising and lowering said frame, whereby said tools are raised and lowered to facilitate loading of said chucks, and a crank for simultaneously turning said cams to place different portions of said cams of different thicknesses in engagement with said frame portion, said crank extending outwardly. from said machine beyond said frame.

- PATENTEDFE 9 9m sum 3 OF 7 mi 1 W16.

I N VEN TOR.

' PATENTEU FEB 9197! SHEET t UP 7 INVENTOR. Roberf W Murdock 1 IAP'ATENIQED m 9 m J 'smisaFf INVENTOR. Robe n W. Murdock WELDING CART FOR WELDING A PLURALITY F STUDS TO A BEAM FLANGE. OR OTHER SURFACE This invention relates to a welding machine for end welding studs to a workpiece and more a particularly for end welding shear connectors to a structural beam.

Shear connectors have found wide acceptance for use in composite structural beam and concrete construction. This combination has been used, for example, in bridge construction, highway construction, particularly for overpasses and the like, buildings, and many specific applications where a higher strength-to-weight ratio is desired, such as for the domes of underground fuel tanks. In most applications, the shear connection studs are welded to the beam close together in rows with the rows also being closely spaced, resulting in a large number of studs being use used for each beam. Heretofore, while shear connection studs have been end welded to the beam in much less time than by the use of any other technique for fastening the studs to the beam, nevertheless, such process has been time consuming, particularly in view of the fact that the position of each and every stud had to be laid out first and each stud then hand welded at the appropriate location. The hand welded studs also sometimes have been cocked which resulted in nonuniform shear strengthin the resulting composite construction. Further, the studs would sometimes be welded in improper locations and out-of-line, thereby interfering with the placement of reinforcing steel. Hand stud welding also frequently resulted in accessory damage because of operator carelessness, such damage including burning of the stud chucks, bending and breaking of the welding tools, and similar destruction.

The present invention provides a new welding machine for accomplishing the end welding of shear connection studs faster, more accurately, and with more uniform strength. The new machine welds the studs in rows with the studs in each row being spaced at predetermined distances so that each row only has to be spaced relative to the adjacent row and with no other layout or measurements being required. The new machine also enables the studs to be welded in truly vertical positions and in accurate locations, thereby simplifying placement of reinforcing steel. Because handling of the machine is kept to a minimum, damage to the welding apparatus also accordingly is reduced.

The new shear connection welding machine has a number of features which increase the speed of and otherwise improve the welding operation. The machine is mounted on wheels so that it can be moved easily along a beam to which shear connectors are to be welded. The new machine includes a plurality of welding tools by means of which shear connectors in any particular row can be sequentially welded in place automatically, simply by the push of a button. The tools are movable transversely of the machine so that the studs can be welded in any predetermined position at any desirable location and are adjustable vertically for accommodating studs of different lengths. The new welding machine incorporates a unique chuck design by means of which studs can be loaded in the chucks from the front of or the side, which requires minimum re raising of the welding tools for loading purposes to further speed up the welding operation. The machine also has a simpler and easier arrangement for raising the tools for loading purposes, with a single crank being capable of accomplishing this result and with means being provided to brake the machine when raised.

The new welding machine also has an outrigger rack which enables shear connection studs to be welded completely to the end of a beam. The new machine also has a supply cart supported on and guided by the beam for holding studs and ferrules in an easily accessible position to increase further the rate of welding.

It is, therefore, a principal object of the invention to provide a welding machine having the features and advantages outlined above.

Other objects and advantages of the invention will be apparent from the following detailed description of preferred embodiments thereof, reference being made to the accompanying drawings, in which:

FIG. 1 is a view in perspective of the welding machine according to the invention,.positioned on a structural beam to be used in compositeconcrete and beam construction. with an outrigger rack attached to an end of the beam;

FIG. 2 is a fragmentary front view in elevation of the welding machine and beam of FIG. .1, with the machine being in welding position; i

FIG. 3 is a side view in elevation, with parts broken away and with parts in cross section, of the welding machine in welding position;

FIG. 4 is a detailed view in crosssection taken along the line 4-4 of FIG. 2;

FIG. 5 is a detailed view taken along the line 5-5 of FIG. 2;

FIG. 6 is a fragmentary side view in elevation, with parts broken away and with parts in cross section, of a stud chuck used with each of the welding tools of the welding machine. with a portion of a stud shown in dotted lines ready to be inserted;

FIG. 7 is a view in horizontal cross section taken along the line 7-7 of FIG. 6;

FIG. 8 is a side view in elevation of the stud chuck of FIGS. 6 and 7, with a portion of a stud shown in solid lines in welding position;

FIG. 9 is a side view in elevation of the outrigger rack of FIG. 1 connected to the structural beam and with the welding cart shown in dotted lines on the rack;

FIG. 10 is a detailed, fragmentary view in cross section taken along the line 10-10 of FIG. 9;

FIG. 11 is a view in perspective of a welding supply cart used with the welding machine of FIGS. l-3;

FIG. 12 is a view in perspective of an electrical loop apparatus used with the s welding machine of FIGS. I-3 for certain sizes of studs; and

FIG. 13 is a somewhat schematic plan view of a slightly modified welding machine.

Referring to the drawings, and more particularly to FIG. 1, a welding machine according to the invention is indicated at 10. The machine 10 is moved along a structural beam 12 a to end weld shear connection studs 14 to the beam 12 in rows, there being four studs to a row in this instance. Concrete is then poured over the beam 12 and the studs 14 in a composite construction, as more fully so shown and discussed in U.S. Pat. No. 2,987,855 to Singleton et al. The studs 14 in each of the rows are close together and the rows are also spaced rather closely so that many of the studs 14 are used with each of the beams 12 and any decrease in the time for welding each stud is significant.

The studs 14 can be welded to the very end of the beam 12 by means of an outrigger rack 16 which is removably connected to the end of the beam 12 and which supports the machine 10 beyond the end of the beam during the final operation. Further, to facilitate the welding operation, a supply cart 18 (FIG. 11 is pulled along behind the machine 10, the cart being guided by the beam and containing welding supplies including more of the studs 14 as well as ceramic ferrules 20 which surround the welding end of the stud 14 (FIG. 1) during the welding operation, as is well known in the art.

The machine 10 basically includes an electrical control box 22 which is electrically connected to a remote power source and controls current for the machine. The box 22 supported on a main frame 24, the rear of which is supported by rear wheels 26 through legs 28 and the front of which is supported by front wheels 30 and front legs 32. A plurality of e welding tools 34 in this instance four, are mounted on the front of the frame 24 and are designed to weld the shear connected studs 14 in a row transversely of the beam 12. Referring more specifically to FIG. 3, each of the tools 34 is connected by a web 36 to a tubular support 38 of rectangular configuration which receives an upright rectangular post or support 40. A hand screw 42 is threadedly engaged in in the rear of the tu bular support 38 and can be turned to engage the upright support 40 and thereby hold the tool 34 in any desired vertical position. In this manner, the tool 34 can accommodate studs of varying lengths, such as from 4 to 8 inches.

Each of the vertical supports 40 is attached to a generally U- shaped supporting foot 44 which is slidably supported on guide rails 46 (FIG. 4) attached to the frame 24. The guide rails 46 form a slot 48 in which is received an inverted T-nut 50. The T-nut 50 is in turn is engaged with a vertical connecting bolt 52 which extends completely through the vertical support 40 and is engaged with an'adjusting knob 54 (FIG. 3). When the knob 54 is loosened, the T-nut 50 and the supporting foot 44 can slide relative to the guide rails 46 so that each of the tools 34 can be adjusted transversely of the welding machine 10 and the beam 12 to any desired position. Once the tools 34 are properly positioned, the knobs 54 are tightened to hold the tools 34 in their correct positions, until a change is again desired. Usually, when the tools 34 are correctly positioned vertically and transversely, they will remain in those positions'during the welding of the entire beam 12 or perhaps several beams.

' The welding tool 34 is shown somewhat schematically in FIG. 3 and is generally of the type shown, for example, in the copending application of Mowry and Valeri, Ser. No. 354,786. The tool basically includes a plunge rod 56 urged downwardly by a plunge spring 58 and connected by a clutch arrangement indicated at 60 to a core 62 associated with a liftin coil 64. A plunge dampener indicated at 66 is used to soften the downward stroke of the plunge rod 56 to reduce splatter and produce a better weld,'as discussed more fully in the above-identified application. A stud chuck 68, to be discussed in detail subsequently, is connected to the plunge rod 58 through a suitable threaded connection 70. Current is supplied to the chuck 68 by a suitable flexible conductor 72 plugged into the control box 22. Similarly, current is supplied to the lifting coil 64 by a flexible conductor 74 which is also plugged into the control box 22.

In the operation of the tool 34, with the stud 14 in contact with the beam 12, the lifting coil 64 is activated to withdraw the stud from the beam. At the same time, power is supplied to the chuck 68 to strike an are between the stud and the beam. After-a predetermined period, the lifting coil 64 is shut off and the plunge spring 58 then forces the stud against the beam. The molten metal formed by the are then solidifies to complete the weld.

When one of the shear connection studs 14 is held by the chuck 68 in welding position, as shown in FIG. 3, the end of the stud is engaged with the beam 12 with the plunge spring 58 being compressed slightly. Because of this compression and engagement of the stud 14 with the beam 12, it is very difficult to load the stud 14 into the chuck 68 without raising the chuck 68 and the tool 34. Means for accomplishing this are shown more fully in FIGS. 2, 3, and wherein a cam and crank device indicated at 76 is employed to raise the entire front end of the machine and thereby enable the studs 14 to be engaged with the chuck 68 without-touching the beam. Toward this purpose, the front wheels 30 are rotatably mounted on an axle 78 by roller bearings 80 (FIG. 2) with the axle in turn extending through slots 82 in the bearing legs 32 extending downwardly from the frame 24. The slots 82 are closed at the lower ends a by end bars 84 which are bolted to the ends of the legs 32. Cams 86 are affixed to the axle 78 immediately beyond the supporting legs 32 and rotate with the axle 78 when turned by a crank 88 FIGS. 1 and 2). The earns 86 contact roller rollers 90 suitably rotatably mounted by stub axles 92 on thesupport legs 32 above the axle 78. When the crank 88 is moved from its downward position as shown in FIGS. 2 and 3 to its upward position (FIG. 1) the thickest parts of the earns 86, having flat portions, are positioned between the axle 78 and the stub axles 92, thereby forcing apart the axles. This forces the stub axles 92 and the rollers 90 upwardlyalong with the support legs 32 to which they are attached. Consequently, the entire front of the cart 10 is raised, rotating about the rear wheels 26, with the upward movement being equal to the particularly when the studs 14 are pushed into the chuck 68 and a pushing force is exerted on themachine-10. To prevent the machine from rolling in such an instance, brake shoes 94' with layers of friction material 96 are fastened to the legs 32 by supporting arms 98, there being two of the brake shoes 94 for the two front wheels 30. The brake shoes 94 are so positioned that when they are raised with the supporting legs 32, they engage the wheels 30 to prevent rotation thereof. This locks the machine 10 firmly in place. When the crank 88 is turned 180, the brake shoes 94 are lowered along with the supporting legs 32 and are thus free of the front wheels. By this time, the studs will have been loaded in the chucks and will engage the beam 12 in the welding position. After the studs are welded, the machine is then pushed away from the studs to disengage them from the chucks and is then easily rolled to the next position. Once again, the crank is turned 180 to raise the machine 10 and engage the brake shoes 94 with the front wheels 30 during the next loading operation.

The machine 10 has a lifting frame 100 and a lifting hook 102 (FIG. 1) attached to the frame-24 near the center of gravity. These enable the machine 10 to be transported easily from one beam to another by a hoist or crane.

Referring now particularly to FIGS. 6-8, the stud chuck 68' will be discussed in detail. The chuck 68 is particularly useful with the machine 10 because the studs 14 can be loaded from the front or side rather than from the bottom, as has heretofore been the case. The front loading is both easier and requires that the machine 10 be raised to a lesser extent than otherwise necessary. Thechuck 68 basically includes a copper electrical block or member 102, which is screwed or otherwise suitably attached to the connection 70 and, a steel pressure block or member 104 having legs 106 which are pivotally connected to the block 102 by a pin 108. The block 104 also forms an opening or notch 110 to receive a shank 112 of the stud 14, just below a head 114. The pressure block 104 also preferably includes two hardened metal inserts 116 (preferably made of a carbide steel) which actually contact the head 114 of the stud 14 to minimize wear on the pressure block 104. Through the inserts 116, the pressure block 104 presses the head 114 of the stud 14 into electrical contact with the electrical block 102 by suitable resilient means urging the pressure block 104. toward the block 102. The resilient means in this instance constitutes a spring 118 compressed between the electrical block 102 and the pressure block 104 on the side of the pivot 108 opposite the stud-receiving opening 110. The spring 118 is held in place by a retaining rod 120 which is threadedly engaged with the pressure block 104 and extends through an opening 122 in the electrical block 102 with an adjustable stop or nut 124 threaded above the block 102. The stop 124 limits the extent of movement of the blocks 102 and '104 toward one another. The stud 14 can be relatively easily loaded in the chuck 68 from the position shown in FIG. 6 and, when loaded, the entire upper surface of the head 114 is maintained in good electrical contact with the block 102 by pressure exerted through the inserts 116.

After the studs 14 are loaded in the chucks 68 and are welded in place by the operation of control switches on the box 22, the machine 10 is pushed off the studs 14 and rolled along the beam 12 to the next position where the operation is repeated. During the movement of the machine 10 to the nextposition, its path is controlled by a pair of front guides 126 and a pair of rear guides 128. The front guides 126 include rollers 129 rotatably held by supports 130, which supports extend above the frame 24 and are adjustably affixed thereto, for example, by bolt bolts extending through slots in the supports. in

this manner, the supports 130 and the rollers 129 rotatably held by supports 130, which supports extend above the frame 24 and are adjustably affixed thereto, for example, by bolts extending through slots in the supports. in this manner, the supports 130 and the rollers 129 can be moved in and out for different widths of beams so that the rollers 129 will contact the edges of the beam flanges to locate the machine in a proper position transversely of the beam. The rear guides 128 similarly include rollers 132 which are rotatably held by suitable supports 134 adjustably affixed to, a rear flange 136 which depends from the frame 24. The supports 134 similarly are adjustably affixed to the flange 136, as by means of slots and bolts, so that the rollers 132 can be adjusted inwardly and outwardly to accommodate beam flanges of different widths.

When the studs 14 are to be welded to the very end of the beam 12, a problem is presented because the studs cannot ordinarily be welded closer to the endthan the length of the machine 10. Where the studs are to be welded to the end, however, this can be accomplished by means of the unique outrigger rack 16 (see also (FIGS. 9 and 10) affixed to the end of the beam 12. The outrigger rack 16 includesa platform or support 138 and side flanges or rails 140 which cooperate with the wheels 26 and 30 to properly guide the machine 10 relative to the beam 12. The guide rails 140 are spaced apart by the platform 138 a distance equal to that of the wheels so that the outrigger 16 can be used with any width of beam. While the outrigger 16 can be attached to the beam 12 in any suitable manner, for purposes of illustration, the outrigger includes a generally vertically extending leg 142 having a yoke 144 supporting oppositely acting adjusting screws 146 which are screwed toward one another to firmly engage the web of the beam 12. A threaded stop member 148 is provided on a lower portion of the upright leg 142 and can be screwed inwardly and outwardly relative to the leg 142 to place the platform 138 and the rails 140 in the same plane as the upper flange of the beam 12. The leg 142 actually is at an angle of less than 90 to the rails 140 because the end of the beam 12 is not always truly perpendicular and, if the lower portion protrudes, the rails 140 would tilt upwardly if the leg 142 were perpendicular. Hence, the angle of the leg 142 and the adjustable stop 148 accommodate beams terminating in nonperpendicular, protruding ends. A suitable strut 150 connects the outer end of the platform 138 and the lower end of the leg 142 to complete the support for the rails 140.

To increase the speed of the welding operations, the supply cart 18 is supported on and guided by the beam and is pulled behind the machine 10, this cart being shown in FIG. 11. The cart 18 basically includes two bins 152 and 154, the former containing the shear connection studs 14 and the latter containing the ceramic ferrules 20. Because the studs are much heavier than the ferrules, the stud bin 152 is mounted directly on a platform 156 while the ferrule bin 154 is supported by the stud bin 152 by means of a strip hook 158. The bins and the platform 156 are supported on the beam 12 by flanged wheels 160 which are supported by leg members 162. These are adjustable adjustably affixed to the platform 156 by a slot and bolt arrangement to enable the wheels 160 to be moved inwardly and outwardly to engage the edges of the flange of the beam 12. The legs 162 are sufficiently high to enable the cart 18 to clear the previously welded shear connection studs 14.

For studs of certain sizes and particularly heavier studs, it is desirable to establish an electrical field around the welding arc struck between the stud and the beam in order to stabilize this are. For this purpose, an electrical look indicated at 164 in FIG. 12 is used. The loop 164 includes a heavy main conductor 166 with connectors 168 which are plugged into the control box 22 and receive current 'to establish an electrical field around the studs being welded. The conductor'166 extends through copper side tubes 170 with the portion of the conductor 166 between the tubes being suitably fastened by clips 172 to adjustable cross bars 174 so that the conductor will clear the previously welded studs. The only really functional part of the electrical loop 164 constitutes that portion of the conductor 166 in the tubes which is closest to the studs being welded. The ends of the tubes 1,70 opposite the cross bars 174 have supporting braces 177 which are bolted or otherwise suitably affixed to the frame 24 in place of the front outrigger guides 126. The front of the machine 10 is guided by the tubes 170 which are adjusted to be positioned along the edges of the beam 12. Hence, the machine is adequately guided even though the front guides 126 are removed.

In some structural'applications, it is desired to weld the shear connection studs in rows which lie transversely to the beam, at angles other than 90. For such applications, a welding machine of the type designated generally at 178 in FIG. 13 can be employed. The machine 178 is similar in most details to the machine 10 except that the welding tools 34 and the guide members 44 and 46 are mounted on a pivot plate 180 which is pivotally connected to the frame'member 24 by a pivot bolt 182. In addition, the stud chucks 68 can be pivoted with respect to the tools 34 simply by turning them with respect to the connections 70 and subsequently tightening the lower nuts constituting part of these connections.

In the operation of the welding machine 178, the pivot plate 180 is turned relative to the frame 24 to the desired angle which is equal to the angle of the'row of shear connection studs to be welded to a beam. The bolt 182 is then tightened. Subsequently, the tools are raised to their proper heights by the knobs 42 so that'the studs 14 will slightly compress the plunge springs 58 when engaged in the chucks 68 and in welding position. The tools are then adjusted transversely of the beam to the desired positions by means of the knobs 54. For the transverse adjustment, it maybe desirable to am make the guide blocks 46 longer than for the machine 10 in order to assure that the end tools 34 can be moved to the edges of the beam when the plate 180 is to be pivoted to an acute angle. After the tools 34 are adjusted, the chucks 68 are moved to positions parallel to the longitudinal extent of the beam. This is important to enable the machine 178 to be pushed off the studs after they are welded to the beam so that the machine can be rolled parallel to the beam to the next position.

Various modifications of the above described embodiments of the invention will be apparent to those skilled in the art, and it is to be understood that such modifications can be made without departing from the scope of the invention, if they are within the spirit and the tenor of the accompanying claims.

l claim:

1. Apparatus for welding a plurality of studs to a structural beam, said apparatus including a frame, a plurality of welding tools carried by said frame and having chucks to receive the studs, a pair of rear wheels connected to and supporting a rear portion of said frame, a pair of frontlwheels, an axle, bearing means rotatably supporting said front wheels on said axle, a pair of front legs depending from said frame, a said legs having generally vertically extending slots therein to receive said axle, a pair of cams mounted on said axle adjacent said legs, a pair of rollers rotatably mounted on said legs above said s axle and positioned to contact said cams in all positions thereof, and a crank for simultaneously turning said cams and said axle to position portions of said cams of different thicknesses between said axle and said rollers to raise and lower said legs and to move the frame in an 'arcuate path around the rear wheels, whereby said tools are raised and lowered to facilitate loading of the chucks.

2. Apparatus for welding a plurality of studs to a structural beam, said apparatus including a frame, a welding tool carried by said frame and having a chuck to receive the studs, a pair of rear wheels connected to and supporting a rear portion of said frame, a pair of front wheels, an axle, bearing means rotatably supporting said front wheels on said axle, a pair of front legs depending from said frame, a pair of cams mounted on said axle adjacent said legs, a pair of rollers rotatably mounted on said legs above said axle an and positioned to contact said came in all positions thereof, and means for turning said cams and said axle to position portions of said cams of different thicknesses between said axle and said rollers to raise and lower said legs and to move the frame in an arcuate path around the rear wheels, whereby said tools are raised and lowered to facilitate loading of the chucks.

3. Apparatus for welding a plurality of studs to a structural beam, said apparatus including a frame, a welding tool carried by said far frame and having a chuck to receive the studs, a first wheel rotatably supported by an axle, with the axle being in fixed relation with respect to said frame, a second wheel, an axle rotatably supporting said second wheel, a leg depending from said frame, said leg having a generally vertically extending slot therein to receive said axle, a cam mounted on said axle adjacent said leg, contact means mounted on said leg above said axle and positioned to contact said cam, and a crank for turning said cam to position portions of said cam of different thicknesses between said axle and said contact means to raise and lower said leg and said frame, whereby said tool is raised and lowered to facilitate loading of the chuck.

4. Apparatus for welding a plurality of studs in a predetermined pattern to a structural beam, said apparatus comprising a welding machine including a frame, wheels engageable with the frame to support the frame above the beam, a plurality of end welding tools mounted on said frame in predetermined positions, a loop extending from said machine around and in front of said welding tools and having substantially parallel straight portions on each side of said tools, means adjustably supporting said loop on said frame, means holding the end of the loop which is away from said machine above said beam a distance at least as great as the length of previously welded studs in order for said loop to clear said studs, and means for supplying power to said loop when studs are to be welded to the beam.

5. Apparatus for welding a plurality of studs to a structural beam, said apparatus including a frame, a plurality of welding tools carried by said frame and having chucks to receive the studs, a pair of rear wheels connected to and supporting a rear portions portion of said frame, apair of front wheels, an axle, bearing means rotatably supporting said front wheel wheels on said axle, a pair of front legs depending from said frame, said legs having generally vertically extending slots therein to receive said axle, a pair of cams mounted on said axle adjacent said legs, a pair of rollers rotatably mounted on said legsabovc said axle and positioned to contact said cams in all positions thereof, a crank for simultaneously turning said a cams and said axle to position portions of said cams of different thicknesses between said axle and said rollers to raise and lower said legs and to move the frame in an arcuate path around the rear wheels, whereby said tools are raised and lowered to facilitate loading of the chucks. a brake shoes for each of said legs, and arms supporting said brake shoes by said legs for movement therewith, said brake shoes being in position to engage and hold said front wheels a when said legs are in the raised position.

6. Apparatus for welding a stud to a workpiece. said apparatus including a frame, a welding tool carried by said frame, a wheel at least partially supporting said frame and said tool, means for providing relative vertical movement between said wheel and said frame to raise said frame relative to said wheel to facilitate loading of said tool, a brake shoe, and means supporting said brake shoe in a fixed position relative to a said frame, said brake show shoe being positioned to be free of said wheel when the frame is in a lower position and to be engaged with and prevent rotation of said wheel when the frame is in the raised position.

7. Apparatus for welding a plurality of studs to a beam in a predetermined pattem', said apparatus comprising a frame, a plurality of welding tools carried by said frame and having chucks to receive the studs, rear wheel means supporting a rear portion of said frame, a pair of front wheels, a pair of cams rotatable about a common axis in a fixed position relative to said front wheels and engageable with a portion of said frame for raising and lowering said frame, whereby said tools are a raised and lowered to facilitate loading of said chucks. and a crank for simultaneously turning said cams to place different portions of said cams of different thicknesses in engagement with said frame portion, a said crank extending outwardly from said machine beyond said frame.

UNITED STATES PATENT OFFHIE CERTIFICATE OF CORRECTION Patent No. 3, 552,484 Dat wry 9. 1971 Inventods) Robert W. Murdock It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Attorneys Hall & Houghton Column 1, line 48, insert structural before beam; line 59, delete "re".

Column 2, line 41. delete "a", second occurrence; line 68, delete "e".

Column 3, line 65, insert before FIGS. 1 and 2.

Column 6, line 52, delete "a"; line 56. delete "9'': line 72, delete "an".

Column 8, line 4, delete "a", second occurrence: line 9 delete "a" after the word shoe; line 22, delete "show"; and line 37, delete "a".

Signed and sealed this 1 7th day of August 1971 (SEAL) Attest:

EDWARD M.FLETCHER,J'R. WILLIAM E. SGHUYLEH, J Attestlng Officer Commissioner of Patent FORM PO-IOSCHO-SQ) USCOMM-DC 0031 Q .5 GOVERNMENT HUNTING OPTIC! H69 0- 

1. Apparatus for welding a plurality of studs to a structural beam, said apparatus including a frame, a plurality of welding tools carried by said frame and having chucks to receive the studs, a pair of rear wheels connected to and supporting a rear portion of said frame, a pair of front wheels, an axle, bearing means rotatably supporting said front wheels on said axle, a pair of front legs depending from said frame, a said legs having generally vertically extending slots therein to receive said axle, a pair of cams mounted on said axle adjacent said legs, a pair of rollers rotatably mounted on said legs above said s axle and positioned to contact said cams in all positions thereof, and a crank for simultaneously turning said cams and said axle to position portions of said cams of different thicknesses between said axle and said rollers to raise and lower said legs and to move the frame in an arcuate path around the rear wheels, whereby said tools are raised and lowered to facilitate loading of the chucks.
 1. Apparatus for welding a plurality of studs to a structural beam, said apparatus including a frame, a plurality of welding tools carried by said frame and having chucks to receive the studs, a pair of rear wheels connected to and supporting a rear portion of said frame, a pair of front wheels, an axle, bearing means rotatably supporting said front wheels on said axle, a pair of front legs depending from said frame, a said legs having generally vertically extending slots therein to receive said axle, a pair of cams mounted on said axle adjacent said legs, a pair of rollers rotatably mounted on said legs above said s axle and positioned to contact said cams in all positions thereof, and a crank for simultaneously turning said cams and said axle to position portions of said cams of different thicknesses between said axle and said rollers to raise and lower said legs and to move the frame in an arcuate path around the rear wheels, whereby said tools are raised and lowered to facilitate loading of the chucks.
 2. Apparatus for welding a plurality of studs to a structural beam, said apparatus including a frame, a welding tool carried by said frame and having a chuck to receive the studs, a pair of rear wheels connected to and supporting a rear portion of said frame, a pair of front wheels, an axle, bearing means rotatably supporting said front wheels on said axle, a pair of front legs depending from said frame, a pair of cams mounted on said axle adjacent said legs, a pair of rollers rotatably mounted on said legs above said axle an and positioned to contact said came in all positions thereof, and means for turning said cams and said axle to position portions of said cams of different thicknesses between said axle and said rollers to raise and lower said legs and to move the frame in an arcuate path around the rear wheels, whereby said tools are raised and lowered to facilitate loading of the chucks.
 3. Apparatus for welding a plurality of studs to a structural beam, said apparatus including a frame, a welding tool carried by said far frame and having a chuck to receive the studs, a first wheel rotatably supported by an axle, with the axle being in fixed relation with respect to said frame, a second wheel, an axle rotatably supporting said second wheel, a leg depending from said frame, said leg having a generally vertically extending slot therein to receive said axle, a cam mounted on said axle adjacent said leg, contact means mounted on said leg above said axle and positioned to contact said cam, anD a crank for turning said cam to position portions of said cam of different thicknesses between said axle and said contact means to raise and lower said leg and said frame, whereby said tool is raised and lowered to facilitate loading of the chuck.
 4. Apparatus for welding a plurality of studs in a predetermined pattern to a structural beam, said apparatus comprising a welding machine including a frame, wheels engageable with the frame to support the frame above the beam, a plurality of end welding tools mounted on said frame in predetermined positions, a loop extending from said machine around and in front of said welding tools and having substantially parallel straight portions on each side of said tools, means adjustably supporting said loop on said frame, means holding the end of the loop which is away from said machine above said beam a distance at least as great as the length of previously welded studs in order for said loop to clear said studs, and means for supplying power to said loop when studs are to be welded to the beam.
 5. Apparatus for welding a plurality of studs to a structural beam, said apparatus including a frame, a plurality of welding tools carried by said frame and having chucks to receive the studs, a pair of rear wheels connected to and supporting a rear portions portion of said frame, a pair of front wheels, an axle, bearing means rotatably supporting said front wheel wheels on said axle, a pair of front legs depending from said frame, said legs having generally vertically extending slots therein to receive said axle, a pair of cams mounted on said axle adjacent said legs, a pair of rollers rotatably mounted on said legs above said axle and positioned to contact said cams in all positions thereof, a crank for simultaneously turning said a cams and said axle to position portions of said cams of different thicknesses between said axle and said rollers to raise and lower said legs and to move the frame in an arcuate path around the rear wheels, whereby said tools are raised and lowered to facilitate loading of the chucks, a brake shoes for each of said legs, and arms supporting said brake shoes by said legs for movement therewith, said brake shoes being in position to engage and hold said front wheels a when said legs are in the raised position.
 6. Apparatus for welding a stud to a workpiece, said apparatus including a frame, a welding tool carried by said frame, a wheel at least partially supporting said frame and said tool, means for providing relative vertical movement between said wheel and said frame to raise said frame relative to said wheel to facilitate loading of said tool, a brake shoe, and means supporting said brake shoe in a fixed position relative to a said frame, said brake show shoe being positioned to be free of said wheel when the frame is in a lower position and to be engaged with and prevent rotation of said wheel when the frame is in the raised position. 